1. Field of the Invention
Aspects of the present invention relate to a fuel supply unit, and more particularly, to a fuel supply unit that can vaporize a fuel, and a fuel cell system that employs the fuel supply unit.
2. Description of the Related Art
A fuel cell is an electricity generator that chemically reacts an oxidant and a fuel, to produce electricity. A fuel cell can continuously generate electricity, as long as a fuel is supplied.
A direct methanol fuel cell (DMFC) is a fuel cell that generates electricity, through a reaction between methanol supplied to an anode, and oxygen supplied to a cathode. In a DMFC, the anode and the cathode face each other across an electrolyte membrane. An assembly of the anode, the cathode, and the electrolyte membrane is conventionally referred to as a membrane and electrode assembly (MEA).
The cathode is exposed to an oxidant, such as oxygen in air. The anode is surrounded by a spacer, and vaporized methanol is supplied to the anode, through a plurality of holes formed in the spacer. Electrons are generated at the anode, and the electrons move through an electrical circuit, to the cathode. At this point, when a load is applied to the circuit, work can done using the generated electricity.
A fuel cell is generally part of a fuel cell system. A fuel cell system can be classified as an active-type, or a passive-type, according to how a fuel is supplied to an anode. In the active-type, a low concentration liquid methanol is pumped to the anode.
Passive-type fuel cell systems can include a fuel supply unit. The fuel supply unit vaporizes liquid methanol stored in a cartridge, and then the vapor is supplied to the anode, at room temperature, by diffusion. Passive-type fuel cell systems are often used in mobile devices, because passive-type fuel cell systems generally are smaller in size.
It is generally beneficial for a fuel supply system to evenly supply fuel to an entire surface of an anode. In this way, a rapid initial start-up can be realized, by uniformly supplying vaporized fuel to an MEA.
If the fuel is supplied through a single supply path, it takes time to achieve a uniform concentration of fuel across the anode. Thus, an initial start-up may be delayed. Therefore, there is a need to develop a configuration of fuel supply system that can uniformly supply fuel across an anode of an MEA, in a short time.